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Old Jan 09, 2005, 11:48 AM
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Bill Glover's Avatar
United Kingdom, Bracknell
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Quote:
Originally Posted by Dave Barrow
A 90 on a pipe is pretty loud, the muffled pipes are nice, since they reduce the volume.
I used 3 different muffled pipes on my ST 90 before settling on the Hattori, but none of them could get the motor down to our noise limit (82 dB at 7 metres). There's a lot of prop and induction noise too from big 2 strokes.

But I used the piped 90 to win a couple of unlimited pylon races, turning an APC 10x10
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Old Jan 10, 2005, 10:34 PM
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I bought this pipe on ebay, with header, It said that it will make the engine quiet, but from diagrams I have seen some have a pipe tapering inside pipe, when I look into the end of mine its just a hollow pipe, so I dont think its goning to be very quiet.. I'll see what happens, as I am going to run the engine in this comming weekend and then I'll fit/tune the pipe.. I will post the results, also I'm greatful to all who replied as feedback is important, I admittledly have no experience with pipes at all, so this is going to be a learning curve... I will post the results when its tuned...wish me luck...lol
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Old Jan 11, 2005, 03:00 AM
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Tony Oliver's Avatar
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majic12 - these types of pipe are not meant to silence the engine, but to improve the power output. The running engine's exhaust pulses sets up a wave within the carefully shaped pipe which has the effect of pulling the exhaust gases out of the engine. It's the opposite of a supercharger, I suppose. This gets the improvement in the fresh fuel/air mix going into the engine free of exhaust gases which may still remain - better and more fuel/air charge = more power. Some certainly do run quieter, but I'm not sure why that should be.
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Old Jan 11, 2005, 08:17 AM
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Quote:
Originally Posted by majic12
I bought this pipe on ebay, with header, It said that it will make the engine quiet, but from diagrams I have seen some have a pipe tapering inside pipe, when I look into the end of mine its just a hollow pipe, so I dont think its goning to be very quiet.. I'll see what happens, as I am going to run the engine in this comming weekend and then I'll fit/tune the pipe.. I will post the results, also I'm greatful to all who replied as feedback is important, I admittledly have no experience with pipes at all, so this is going to be a learning curve... I will post the results when its tuned...wish me luck...lol
What size pipe did you get, that is important as well, but yes, most of the muffled pipes have a flat (90 degree) back. I suspect yours might not be muffled. You will know in a hurry with a .90!

Mike
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Old Jan 11, 2005, 12:45 PM
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Just to be clear, a tuned pipe also sends a pressure pulse back towards the exhaust port just before it closes. This pushes back some of the new (unburnt) fuel/air mixture that would otherwise be lost, and slightly increases the compression ratio.

If the pipe length is wrong the timing of the low and high pressure pulses doesn't match when the exhaust port is opening and closing. In the worst case this can result in exhaust gases being pushed back in to the cylinder, and fresh fuel/air mix being sucked out!

A simple tuned pipe only increases power and rpm and will make the motor quite a bit more noisy. Just about the only place you see pipes like this are on control line speed models and FAI F3D pylon racers. 99% of pipes sold nowadays are 'quiet' or 'muffled' pipes which have an expansion chamber (=silencer) tacked on after the reflector part. They are also (generally) designed to work over a relatively wide rpm range, partly to make them easier to set up but also so they give some boosting effect at less than full throttle.

A pure 'speed' pipe will often only work over a very narrow rpm band. So narrow in fact that the engine sometimes won't peak out on the ground ... it relies on the in-air rpm increase to get the engine 'on pipe'. You would never use a pipe like this with a throttled r/c engine.
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Old Jan 11, 2005, 12:48 PM
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PS a good 'quiet' pipe can be quieter than a standard muffler simply because the silencer section has a much bigger volume (and is often baffled). I've always used quiet pipes on my models from .36 upwards, and I have a couple of .20 size ones too.
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Old Jan 11, 2005, 01:03 PM
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A pure 'speed' pipe will often only work over a very narrow rpm band. So narrow in fact that the engine sometimes won't peak out on the ground ... it relies on the in-air rpm increase to get the engine 'on pipe'. You would never use a pipe like this with a throttled r/c engine.
Yep - and man is it cool when they "come on the pipe" The plane begs for mercy!

Mike
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Old Jan 11, 2005, 01:53 PM
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The pipe I got is referenced under the heading of tuned pipes at the mac's website , not under the section of quiet pipes, and since there is no baffle inside its going to be LOUD I guess.. the confusion I am faced with , is that the mac's website explains how to tune it, ..by running open faced exhaust..record the rpm , then mounting the pipe/header , keeping cutting 1/4" inch off till you peak out the rpm's etc..but now I have been advised that due to the timing of this engine(142 degrees) it will make maxium power lower than its peak rpm of about 14000- 16000, down somewhere around 11,000 this sort of contradicts the tuning information and running it lower than peak rpm, doesnt sit well with me.
Tonyo - I didnt intensionally want a quiet pipe, I wanted something to make my F4 Phantom prop jet really haul around the skies - the advert on the pipe just said it will make it quiet as well as peak in rpm, I just thought if theres such a thing its an extra benefit..but truthfully I love hearing a motor peak out
pada4u..I hope I have just such a result, -have the plane hanging on for mercy
Bill Glover- if it produces its power in a narrow powerband.. I just hope thats somewhere around full throttle!!
Dave Brown..the brand is a mac's pipe suited for a .90 - 1.20 or 1.30 and my plane comes in at just over 10 .5 lbs so I hope thats gonna be a reasonable power to weight/ drag etc
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Old Jan 11, 2005, 02:08 PM
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Quote:
Originally Posted by pda4you
Yep - and man is it cool when they "come on the pipe" The plane begs for mercy!

Mike
We used to fly small r/c planes indoors at the Olympia exhibition centre in London as part of the Model Engineer Exhibition (later renamed the International Model Show). One year some guys brough a control line speed model and flew that in one of the slots

I think it was 'only' a .15 class model but it was pretty scary indoors, most of the r/c fliers (me included) found a pillar to stand behind!

But it was very interesting to see it do half a dozen laps with a very sick sounding engine ... slowly getting faster ... until wham, it came on-pipe and off it went
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Old Jan 11, 2005, 02:12 PM
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Quote:
The pipe I got is referenced under the heading of tuned pipes at the mac's website , not under the section of quiet pipes, and since there is no baffle inside its going to be LOUD I guess.. the confusion I am faced with , is that the mac's website explains how to tune it, ..by running open faced exhaust, record the rpm , then mounting the pipe/header , keeping cutting 1/4" inch off till you peak out the rpm's etc..but now I have been advised that due to the timing of this engine(142 degrees) it will make maximum power lower than its peak rpm of about 14000- 16000, down somewhere around 11,000 this sort of contradicts the tuning information and running it lower than peak rpm, doesn’t sit well with me.
The OS Hanno motor was the same, as I recall it developed it's power at a pretty low RPM. So you just prop it appropriately.

Follow the procedure (I don't know anyway to do it otherwise) and when the RPM drops lengthen the pipe (in the silicone connectors) until you hit that peak again. Remember all this is based on that exact prop, fuel and plug. If you change anything you may not be in that peak. You can tell when they come on the pipe trust me!

Mike
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Old Jan 11, 2005, 05:11 PM
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Thanks for including the bit about 'the pressure pulse back to the exhaust port' Bill. I somehow didn't get that bit in.

All in all, it's a lovely sound when the pipe goes 'on song'. Trouble is we modellers are the only ones who appreciate it. Mine on the MDS had no trouble throttling down but needed a dive to get it back up to speed on the few outings it got - and I never did build the F15 pusher as we lost the use of the runway. Sad.
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Old Jan 11, 2005, 05:29 PM
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Quote:
Originally Posted by tonyo
All in all, it's a lovely sound when the pipe goes 'on song'. Trouble is we modellers are the only ones who appreciate it
Never a truer work said!

I used to fly pylon, and four motors howling on the start line really is music to the ears! Actually four TD 020s screaming away indoors at Olympia before the start of a heat there wasn't a bad substitute!!
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Old Jan 11, 2005, 05:33 PM
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Adelaide, South Australia
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Quote:
Originally Posted by Bill Glover
I think it was 'only' a .15 class model but it was pretty scary indoors, most of the r/c fliers (me included) found a pillar to stand behind!

But it was very interesting to see it do half a dozen laps with a very sick sounding engine ... slowly getting faster ... until wham, it came on-pipe and off it went
If you'd like to hear and see "only" a .15 speed model come on the pipe then check out this video
http://www.privett.plus.com/record/control_line.htm
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Old Jan 13, 2005, 07:45 AM
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Sometimes I just do not understand all of this "break in" stuff. I will run 1 tank thru a new engine and then go fly. I have never had any problems with my engines.

This break in period is over blown IMHO. I have raced motorcross in the 80's and we never "broke in" a new engine.

Run a tank then fly.




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Old Jan 13, 2005, 08:23 AM
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This break in period is over blown IMHO. I have raced motorcross in the 80's and we never "broke in" a new engine.

Run a tank then fly.
On modern sport power engines you are likely very close to right. OS is likely the king at this. Their engines tend to need very little run in time.

I guarantee if you tried this with high performance engines you would not get much of a flight in as they will not hold a setting under load. This will ensure a lean or rich run. Both bad for ABC engines.

I just won't fly and engine until it holds a reasonable top end, and idle well enough not to dead stick.

All engines need a break in - I know my buddy who races motocross does this with all new bikes/engines.

I guess the real test would be to see how long a properly broken in engine lasts, vs a stick it in the plane and go fly. Some of us never reach that stage of an engines life.

Mike
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